Method for jet smelting



Sepf- 5, 1950 P. E. CAVANAGH 2,951,756

METHOD FOR JET SMELTING Filed May 16, 1958 2,951,756 Patented Sept. 6,1960 METHD FOR JET SMELTING Patrick Edgar Cavanaugh, 320 Laird Blvd.,Montreal, Quebec, Canada Filed May 16, 1958, Ser. No. 735,783

18 Claims. (Cl. 75L-40) This invention is directed to the treating ofiron` ore, and particularly magnetite ores, for the production ofmetallic iron therefrom. Specifically, the invention relates to theproduction of metallic iron from magnetiteores in linely -dividedparticulate form wherein the ore particles are propelled in Va llameduring treating and injected into a furnace bath by impingement of theproducts of combustion upon the surface of such bath.

There have been a number of prior proposals for the smelting ofparticulate ore materials. ln some of these prior smeltingdevelopments,` where iinely divided ore is used, the ore particles havebeen subjected to a reducing action with the particles suspended in acounterow reducing gaseous medium. Such a counterow procedure severelylimits the rate of ore smelting utilizing any reasonably sized furnaceand also necessitates providing substantial and expensive furnacestructures t withstand the high temperatures encountered in operation ofsuch a procedure. These limitations reduce the acceptability forpractical application of these prior smelting proposals. l

' In a number of these prior art smelting developments,

the reaction occurring in reducing the iron ore to metallic iron hasbeen relatively slow due to the use of powdered coal for the combustiblemedium and for the reducing constituent. Of course, there are numerousother smelting proposals including the well known and principally usedblast furnace technique. Discussion of the operation of the well knownVblast furnace need not be set forth. It may be pointed out; however,that the coke used in the blast furnace, among its functions, serves toform a supporting skeleton in the furnace of suficient porosity topermit the gases to flow upwardly through the furnace. With relativelyfine ores mixed with the requisite amount of limestone for ux purposes,the charge would pack together too tightly in the furnace to'permit thenecessary passage of gases.

In the light of the above ore smelting problems, the instant inventionseeks as its primary object to achieve rapid treatment of iron ore infinely divided particulate for-rn, with simplicity in the operatingmethod and a minimum amount of bulky furnace structure being required. 4

It is thus an important object of this invention to pro- Vide animproved method for the treatment of magnetite ores in nely dividedparticulate form to produce metallic iron therefrom.

It is another important object of this invention to pro"- vide anapparatus wherein iron ore mayV be expeditiously treated while suspendedand propelled in combustion products to produce metallic iron therefromand insure separation of the metallic iron and slag from the'gaseousconstituents employed in treating the ore.

A further object of the instant invention is to provide for treatment ofmagnetite ore by initially subjecting ,such ore to an oxidizing actionat a temperature of at `least 2,800" Rand preferably about `3500to,3600f` F. and thereafter toV a reducing action to producefmetalliciron therefrom.

Itis also an object of this invention to provide an iron ore` treatingapparatus embodying a. bath-type furnace having a downwardly directedburner assembly with the ore to be treated being introduced intointimate con# tact with the ilame'or products of combustion from suchVassembly for treatment and to be propelled and impinged up'on thesurface of the bath by such flame or products of combustion.

Another object of this invention is to provide amethod and apparatus fortreating iron ore in a bath-type fi1r-` nace made in accordance with theabove object wherein the ore isinitially introduced into aiirs'ttreating `zone which is oxidizing in character and a second treatingzone is provided between the first zone and the bath with a reducingagent being introduced into the secondi zone.

In accordance with the above object, it is a furtherl object to p rovidea method and such a bath-type furnace apparatuswherein the reducingagent is preheated vbefore its introduction into the second zone, withthe apparatus providing a preheating chamber surrounding the burner. i

An additional object of this invention is to provide in the ore treatingmethodand apparatus `of the above objects for etiicient separation ofgaseous constituents from the metallic iron and slag at the surface ofthen bath by withdrawal of the gases at substantially l tothe directionof impingement of the gases upon the bath surface. p i

The above andother more specific objects of this in-` vention willbecome readily apparent by reference to the following description of aspecific embodiment of the invention taken in conjunction with thedrawing'. In the drawing the single figure` is a diagrammatic sectionalView of a furnace structure made in accordance with the instantinvention and in which the methodof such invention may be carried out.

Before discussing in detail the specific structure shown on the drawing,general referencemay be had toL the overall operational' features ofapplicants invention. In accordance with the invention, a mixture ofpredomi-` nantly magnetite ore and a suitable flux in iinely dividedparticulate form is introduced into the center of a first treating zoneof a downwardly directed combustion flame. The flux is preferably limealthough ground limestone` or' known fluxes used in ore smelting may beemployed. The flame is generated by the combustion of preferably naturalgas and oxygen to provide the requisite high temperatures Vand rapidheating for they ore treatment. An` excess quantity of oxygen isemployed iu the combustion so that the llame will be oxidizing incharacter. A

The" magnetite ore (F`e304) reacts in the oxidizing flame to combinewith the excess oxygen to form hematite or ferric oxide (FeZOS). Thisreaction is exothermic such that heat is liberated which, along with theheat of combustion of the lfuel, produces rapid" heating of the oreparticles. Upon such rapid heating, decreptation and cracking of the oreparticles occurs to` expose a greater surface area to the heating actionand for the subsequent reducing action.

The mixture, including the shattered ore particles, with the iron Ainthe form of ferric oxide, is propelled on with the products ofcombustion into a second treating zone. In this second zone, a reducingagent, preferably natural gas, is added to envelop the products ofcombustion and mixtures entrained therein, and passdownwardly con.-currently therewith towardI the surface of a molten iron and slag bath,`against which the products of` combustion impinge. The highly heated oreparticles assist in. crack ing the natural gas into `carbon monoxide andhydrogen. These constituents rapidly reduce the ferrie oxide to metalliciron. The flux introduced with the ore combines with the gangue portionsofthe ore to form slag as is well known in the art. 1 The flame orproducts'of combustion having the metallic iron and slag constituentssuspended therein impinges upon the surface ofthe molten iron and slagbath such that the molten iron and slag constituents are injected intosuchV bath. The gaseous constituents from theproducts of combustion andreducing agent are separated immediately adjacent they surface of thebath by their Withdrawal outwardly and upwardly away from the bathsurface. The molten iron and slag may be separately tapped from thebath. t

Y Referring to the drawing, an ore treating furnace made in accordancewith the instant invention is illustrated. It will be recognized thatthe particular structure shown is`not intended as representing anaccurate scaled representation of a furnace since several of thecomponents are somewhat diagrammatically illustrated on the draw- Thefurnace structure includes a furnace unit 10 having Walls, providinginteriorly thereof a vertically elongated reducing chamber 11. The lowerpart of unit includes a base 12 supporting a receptacle member 13 whichhas formed in the upper surface thereof a cavity 14 to receive andretain the molten iron and slag as it is produced. The base 12 andreceptacle member 13 are provided with a suitable slag tap 15 and amolten iron tap 16. The iron and slag may be intermittently orcontinuously withdrawn through these taps as desired in operation of thefurnace.

It will be appreciated that in operation of the furnace the receptaclemember 13, retaining the bath of molten iron and slag, will continuouslybe subjected to high ternperatures, such that progressive deteriorationof such member will occur. Thus, the base closing the lower end of thefurnace unit 10 is advantageouslyseparable from the rest of the furnaceto permit its removalrfor repair and replacement as may be necessaryafter prolonged use of the apparatus.

The unit 10 further includes a curtain wall 20 providing a generallycylindrical inner surface 21 which extends downwardly, terminatingimmediately above the molten iron and slag bath cavity A14. This innersurface 21 delines a major portion of chamber 11. f v Y The curtain wallis supported on pillars 24 which define the sides of exhaust gaspassages 25 extending Qutwardly and upwardly from the lower end ofcurtain wall 20 to conduct gaseous exhaust constituents from thereducing chamber 11. These passages 25 extend upwardly on the outer sideof curtain wall 20 and exit at 26 into a header 27 in which dustparticles entrained in the exhaust gases may separate from the gases.The exhaust gases are led oif from header 27 through conduits 28.

The upper end of furnace unit 10 has a cylindrical opening 30communicating with chamber 11 by a downwardly aring or tapering Wallsurface 31 which interconnects the lower end of opening 30 with theupper end of Awall surface 21.

A burner assembly 40 is mounted on furnace unit 10 concentrically withrespect to opening 30. As shown in the drawing, the burner assembly issupported on the upper end of unit 10 by a housing 41 which forms anannular duct 42 surrounding the casing 43 of the burner assembly.Housing 41 is provided with an inlet conduit 44 to introduce a reducingagent, such as natural gas, as will be described in more detailhereinafter. Thus, the reducingV agent, in passing through duct 42, ispreheated by contact with the hot wall of casing 43 and at the same timeexternal cooling of the high temperature combustion chamber casing isprovided. Y

The casing 43 of the burner assembly is divided by a partition memberV45 into an uppercompartment 46 and a lower reaction chamber 47 member45 is provided with a central burner orifice 48. It will further benoted that the lower end of casing 43 defining reaction chamber 47curves inwardly to provide a restricted outlet 49 at the lowermost endof the burner assembly leading into reducing chamber 11.

With reference to the design of the burner assembly, and particularlyconsideringV the design of the burner oriiice 48, reaction chamber 47,and restricted outlet 49, the fluid'flow velocity for proper operationof the ore treating process will be higher than the recognized llamepropagation velocity for Ythe fuel and oxygen mixture being burned. Inorder that the flame will Ynot be blown out at the velocity necessaryfor the products of combustion in carrying out the ore treatment, volumeignition rather than a flame front must -be provided in the reactionchamber 47. This can be accomplished by proper design of the burnerassembly and the introduction of controlled turbulence as obtainable bythe use of obstructions and shoulders in the uid stream. With a properlyproportioned turbulent burner reaction chamber, combustion can be atleast complete by the time the combustion products leave the reactionchamber.

As shown, fuel, such as natural gas, is introduced into mixingcmpartment 46 through a pipe 50, and a combusting supporting medium suchas oxygen introduced into the mixing compartment through a pipe 51.

`The Vburner assembly 40.is provided with a centrally disposed duct 55at the upper end of casing 43 for the introduction of finely dividedparticulate iron ore to be treated. particles immediately above theburner orifice 48 such that these particles pass downwardly through theorifice and into the flame existent below such orifice. Thus, the oreparticles as introduced are centrally disposed and become completelyenveloped in the llame. Y j

The duct 55 leads from an ore supply hopper 56. A suitable gas lock 57is shown disposed between hopper 56 and burner casing 43 to permitdischarging the particulate ore into the burner without pressureexistent in mixing compartment 46 escaping upwardly through duct 55 andhopper 56.

A passage 60 may be provided to recycle molten metallic iron to the ironbath as will be described hereinafter.

Having described structural details of a furnace ernbodying the featuresof the instant invention, reference may now be had to the ore treatingprocess as carried out in such a furnace for producing molten metalliciron from suchV ore. furnace, a supply of finely divided particulate oreof pre-L dominantly magnetite is introduced into hopper 56. The ore ismixed with a suitable flux, preferably lime, to combine in theseparation of gangue portions from the ore being treated. The proportionof flux and its composition may be determined in accordance with theknown principles of iron ore smelting to properly slag oi silica, etc.contained in the particular ore being treated. Y

As is well known, magnetite ore may be upgraded or Vconcentrated bymagnetic separation processes. In the ore treating process of thisinvention, preferably a concentrated magnetite ore containing at least60% iron and ideally less than 10% silica should be used in anessentially dry state. In the extremely rapid heating to which the orein subjected in the reaction chamber, the use of a hard crystallinemagnetite is particularly well suited for treatment in the process. Withsuch an ore the rapid heating will effectively shatter the ore crystalsinto much smaller particles, 4exposing fresh surface to the action ofrthe gases. Further, with regard to the ore and ux mixture introducedfor treatment in accordance with this invention, the mixture should beof aV size'or be crushed to a size below 60 mesh, with not more than 15%below 325 mesh. s l A v l' The particulate ore and iiuxisfed downwardlythrough gas lock 57 and duct 55 into the mixing compartment Thepartition It will be noted that duct 55 discharges the ore In utilizingthe heretofore described Aff'- 46. Oxyg'en, preferably 90 pure, isintroduced through pipe 51 to mix with natural gas introduced throughpipe 50 `as the mobile fuel. The ratio of oxygen to natural gas willjbeapproximately 2 to 1 for stoichiometric combustion, with an excess ofoxygen over this ratio being introduced to result in an excess of oxygenin the cornbustion products such that an oxidizing ame is produced.

The use of oxygen or oxygen enriched air to burn with vthe natural .gasmobile fuel in chamber 47 has definite and special advantages incarrying out the process of the instant invention. By employing such acombus* tion supporting medium, higher temperatures in `a very shortdistance of travel of the iiame are produced than possible with ordinaryair. For one thing, in view of the high nitrogen content of lair, thetotal volume of combustion gases is relatively large Where air providesthe combustion supporting oxygen. This factor alone mili-tates against.achieving the high temperatures and rapid ore heating critical incarrying out ore treatment under this invention. Further, such highervolumes of products of combustion create a problem in separating theiron and slag particles from the exhaust gases such that more dust, etc.is carried out of the furnace through the exhaust gas ducts.

Actually, considering the high temperatures necessary in the process ofthis invention as will be discussed in more detail hereinbelow, it isnear essential that oxygen or at least oxygen enriched yair be employedin the :fuel combustion. An overall economy in operating the oretreating process can resul-t where relatively inexpensive natural gas isavailable and oxygen or oxygen enriched 'air is used. This stems fromthe fact that less fuel will be required to obtain the rapid hightemperature heating of the ore than where the high volume of combustionproducts from air burned fuel are employed. The overall economy isfurther assisted where the high heat content in the exhaust gases isemployed, as for example, in the production of oxygen for use in thecombustion step.

The mixture including ore particles and flux, in passing from duct 55through compartment 46, mixes with the combustible gases lfor-med fromthe natural gas and oxygen and pass therewith through the burner orifice48.

The combustible gases are ignited in reaction chamber 47. The actual ametemperature within this chamber is about 4200 F. to 4500" F. and rapidlyraises the temperature of the ore particles, with increase intemperature being -aided by the reaction of ythe magnetite ore with theexcess oxygen in the combustion products which oxidizes the-ferrosoferric oxide to hematite or ferric oxide. This reaction isexothermic, with t-heheat given off by such reaction furthercontributing to the rapid temperature rise of the ore particles to about3500 F. to 3600 IF. Whereas the flame temperature in compartment 47 ispreferably :between about 4200 F. to 4500" F., it is pointed `out thatthe temperature of the ore particles must be at least 2800 F. for thereaction between the magnetite ore and excess oxygen .to occur.Actually, unless the particle temperature is considerably above 2800" F.the rapid reaction time, which is a major advantage in carrying out theinvention, is not achieved. Thus a particle temperature of about 3500 F.to 3600 F. is preferred. The Vimportance of this exothermic reaction inthe treatment of magnetite ore will be appreciated when it is recognizedthat the heat from this reaction may contribute about 20% of the heatrequired to -reduce to mo-lten metal the iron in, for example, a 66% Femagnetic concentrate.

A particular advantage ilowing from the extremely rapid heating of theore particles results from` the decrepitation and cracking of suchparticles occurring during this rapid heating. This shattering' exposessubstantially greater surface areas of the particles to the hightemperature land excess oxygen in the dame such that 5 the entirequantity of the particles" is brought upV tothe requisite temperature.in a minimum time' as the ame and particles pass downwardly tromreaction chamber 47 through outlet 49. The egaseous combustion productsleave the burner at about 4,000 F.

The gaseous combustion products and mixture suspended therein are thuspropelled downwardly into re. ducing chamber 11. A supply of naturalygas as a reducing agent is introduced through conduit 44 into annularchamber 42. 'This chamber surrounds the lower end of burner casing 43,and accordingly, the reducing `agent is preheated by contact with thehot Wall of the burner casing exteriorly of reaction chamber 47. Thereducing agent, in the form of natural gas, flows downwardlyV throughopening v30` intof reducing chamber. 11,; In such downward flow itenvelops the combustion products and mixture passing through outlet 49such that the two streams ilow concurrently downwardly through -reducingchamber 11. The added natural gas provides a reducing atmosphere toreact with the erric `oxide in the suspended mixture to reduce it tometallic iron.

Theuse of natural gas as a reducing material is particularlyadvantageous in the operation of this invention since the lferric oxidepresent in the oxidizing flame passing from outlet 49 `acts as acatalyst to crack the natural gas (CH4) into hydrogen and carbonmonoxide. These constituents in turn react with the ferrie oxide in re-Vducing it to metallic iron -with` -water vapor and carbon dioxide alsobeing produced. The Water and carbon dioxide react endothermically withthe gas remaining to form further hydrogen and carbon monoxide,resulting in a reduction in temperature at this stage in the process.Such reduction in temperature contributes to the possibility ofutilizing a muc-h simpler and more economical furnace design than whereextremely high temperatures are encountered. The gaseous constituents,slag and metallic iron are propelled downwardly, `by operation of the`downwardly directed burner assembly 40, toward the surface of the moltenbath in cavity 1 4. The gaseous constituents are ygiven suiiicientmomentum by the burner operation such that the metallic iron and slagwill be injected into the bath, resisting the tendency of the gases tocarry these materials laterally and upwardly through Vpassages 25 as thegases are conducted lfrom the furnace.

It will be particularly noted that by the relationship of the lburner tothe passages 25 the direction of movement of the gaseous constituents isturned substantially or reversed immediately adjacent the surface of themolten iron and slagbath. rlhis serves to further promote separation ofthe gases from the metallic iron and slag. The exhaust .gas iiow throughpassages 25 should preferably be below ltwo feet per second to minimizecarry over ofsolid particles trom the furnace chamber l11.

The .downward velocity of the particles entrained in the ame or productsof combustion must be at least 16 feet per second to insure adequateseparation of the iron and slag suspended in the gases. At lowervelocities the dust losses carried out with the gaseous constituents`will be excessive. In order to accelerate .these particles to therequisite velocity for impingement on the surface of the bath, thedownward velocity of the gases in which the particles are entrainedshould be abou-t 40 feet per second or greater. Of course, it will berecognized that the velocity of the products of combustion leaving theburner assembly may be in the order of 600 -feet per second. Suchcombustion products expand rapidly lirnmediately upon exit from theburner assembly, slowing down so that the average velocity may be as lowas 40 feet per second .to impart the requisite velocity to the entrainedparticles. There is no maximum `tiri-ng velocity except that, vdependingon the design of the furnace, the faster tiring velocities will requirea longer furnaceto provide `enough time for the ore to `be properlytreated inpassing through Ithe furnace. p t

Considering the relation of the'natu'ral gas reducing agent to thetiring velocity, it has been found that prefrably the reducing agent,w-hich envelops the ame or combustion products, should have a velocityless than the tiring velocity and specific-ally in the order of betweenand 80%V of the tiring velocity. Under such conditions of operation, theame will assume a desirable cylindrical shape with the outer envelope ofcooler reducing agent moving more slowly than the inner flame orproducts of combustion. Thus, the higher velocity ame or products ofcombustion will tend to draw in or inspirate the reducing agentthereintoto promote the reducing action of the iron oxide.

It has also been found `as an important aspect of this invention thatfor optimum operating conditions, employing natural gas as the mobilefuel and as the reducing agent, it is critical that a ratio of naturalgas reducing agent to natural gas mobile fuel be maintained between1.5:1 and 2:1. For proper theoretical heat balance` in the furnaceoperation, the ratio of reducing agent to mobile fuel should bemaintained at about 1.62: 1.

If furnace operation is carried out substantially below this ratio, laninadequate quantity of reducing gas is provided to carry out the oretreating. On the other hand, if operation is carried out too far abovethis critical ratio, an excessive amount of heat is taken up in thefurnace reactions, etc. so that the' overall process is not properlycarried to completion. It may be computed that utilizing this ratio of1.62: l, a ton of metallic iron produced from magnetite ore (66% Fe)will require approximately 44,250 cubic feet of oxygen and a total of55,800 cubic feet of natural gas. A theoretical heat and materialsbalance may be developed as follows:

Approximate heat balance per ton of metal In Out MM Per- MM Perb.t.ucent b.t.u. cent Gas-55,800 ou. Metal 1.88 a a Ft 55. 0 98. 5 Slag 31 5Oxidation of Hg reduction 24 4 magnetite 0. 60 1.0 Waste gas 44. 25 79.0CO reduction... 0. 06 0.1 Fe;C formation..- 0.32 0. 4 46. 68 T news 9. 316. 6

M aterals balance per ton of metal In Out Primary gas cu. ft.. 21, 300Metal at 4% C -.lbs 2, 000 Secondary gas. .cu. it. 34, 500 Slag .lbs-405 Oxygen cu.ft. 44, 250 Exhaust gas. cu. it 168,500 Ore at 66% Felbs.. 2, 950 Lime lbs..

In initially starting the process, a molten metal bath is provided incavity 14 upon which the downwardly propelled gases will impinge. VAsthe process operates, slag and molten iron will accumulate in the bath,these constituents being continuously or periodically withdrawn lthroughtaps 15 and 16, respectively, as they are formed in the bath.

, The bath is preferably maintained at a temperature of .between 2800 F.and 3000 F. This temperature may beV regulated within limits byadjustment of the distance between the surface of the bath and thehottest point of the flame. It will, of course, be recognized that thelength of thefurnace is dictated for a particular ore charging speed'bythe amount of travel required to heat the ore and,` after the reducingagent is added, the distancenecessary to get proper reduction of theiron oxide. "The removal of the last 10% of the oxygen from the ironoxide may present particular problems in the process of theins'tantinvention. This nal reduction can be elected in the molten bath by Vone-of several mtehods. A'portion of the molten metallic iron, preferablyabout 15% to 50%' of the iron produced may be withdrawn from the bath,the carbon content thereof adjusted and the metal; .still in a.moltenystate, reintroduced into the bath through passage 60. Such recycling ofa portion of the molten metallic iron with the carbon contentappropriately adjusted causes the final reduction of the last 10% of theoxygen in the bath at a rate such that a furnace of given dimensions maybe run at a substantially higher production capacity. The last 10% ofoxygen may also be removed from the bath by the addition to such bath ofcoke. Otherwise, this oxygen may be removed by the addition to theburner of carbon, crushed to a size comparable to that of the ore` andilux particles.

The'regulation of the amount of recycled molten iron or carbon or cokeadded can be adjusted to provide a carbon content in the molten metalliciron in the bath of from 1% to 4%. It is thus possible to produce eithera high carbon product or a low carbon product. Obviously the higher thecarbon goes, the easier it is to obtain removal of the last 10% ofoxygen from the iron oxide. The preferred compromise between carboncontent of the product and removal of the last degree of oxygen from thebath is about 3% to 3.5%.

In order that the ore particles can be most completely reduced tometallic iron, the exhaust gases conducted from the furnace will remainreducing in character and contain some carbon monoxide and hydrogen. Theexhaust gases can thus be burned to preheat the ore prior to itsintroduction into the furnace, or burned and used to produce steam whichcould be employed for the manufacture of oxygenin la standard oxygencompressor plant. A portion of the `exhaust gases, containing carbondioxide and water vapor `can also be recycled into the flame, aiding incracking of the natural gas. Also since the bath temperature is between2800" F. and 3000 F., the exhaust gases will have a comparabletemperature. This heat in the exhaust gases may be used as an energysource for the production of oxygen to be used in the process.

Although the description has been given hereinabove of using natural`gas for the mobile fuel and reducing agent, obviously manufactured gasor other hydrocarbon gas could be substituted. The invention could, asIan alternative to fgas, be operated with kerosene, fuel oil or evenwith powdered coal. Since these latter materials, as fuels, have alonger burning time than gas, a larger furnace would be required to givethe same production.

Thus, in carrying out the instant invention, the use of these latterfuels are Vnotpreferred and have definite disadvantages as will beappreciated.

Further, air preheated at a temperature of about 1500 F. could besubstituted for the oxygen introduced through pipe51. As has beenpointed out, the utilization of air to provide the combustion supportingoxygen would result in a lower'maximum temperature, longer combustiontime and greater gas volume due primarily to the high percentage ofnitrogen in air. A furnace utilizing air could be designed although anoperation of this type is not preferred as it has readily `apparentdrawbacks. Actually, considering the higher temperatures and operatingspeeds possible by burning with oxygen or oxygen enriched air, theoperation costs are indicated to be higher where airis used to supportcombustion.

Whereas arspecific embodiment of the invention has been illustrated anddescribed herein, itV will be readily .recognized that within the scopeof the hereinafter appended claims many variations and changes may bemade, all falling within the purview of the instant invention. It

will also be recognized that the method of this invention capable ofbeing carried out in a variety of different This application is acontinuation-in-part of my prior copending application, Means and Methodfor Jet Smelting, Serial No. 659,663, now abandoned, led May 16, 1957.

What I claim:

1. A method of treating ore to produce metallic iron in a furnace havinga reducing chamber and a molten metal bath beneath such chambercomprising the steps of burning a mobile fuel with the products ofcombustion of such burning directed downwardly to impinge upon thesurface of the bath, introducing a mixture of finely divided iron oreand ux axially of the flame from the burning fuel to be propelledthereby and rapidly heat such mixture, thereafter enveloping the ame andthe mixture suspended therein with a gaseous state reducing agent toiiow concurrently therewith and reduce the iron oxide in the ore tometallic iron, and separating the gaseous constituents from the metalliciron yand slag suspended therein by the impingement of the products ofcombustion upon the surface of the bath.

2. A method as recited in claim 1 wherein the enveloping reducing agentflows at a velocity of between 15% and 80% of the velocity of the tiame.

3. A method of treating magnetite ore to produce metallic iron in afurnace having a reducing chamber and a molten metal bath beneath suchchamber comprising the steps of burning a mobile fuel in an excess ofoxygen to provide a downwardly directed flame zone which is oxidizing incharacter, introducing a mixture of nely divided predominately magnetiteore and ux into the flame to be propelled thereby and rapidly heat suchmixture, thereafter introducing a reducing agent into intimate contactwith the flame and mixture suspended therein to flow concurrentlytherewith and reduce the iron oxide in the ore to metallic iron, andimpinging the products of combustion upon the surface of the bath toseparate the gaseous constituents from the metallic iron and slagsuspended therein.

4. A method as recited in claim 3 further including the step ofpreheating the reducing agent before introducing it into contact withthe llame and mixture.

5. A method as recited in claim 3 wherein the flame is produced byburning natural gas with oxygen and the reducing agent is natural gas.

6. A method as recited in claim 5 wherein the ratio of oxygen to thenatural gas mobile fuel is slightly in excess of 2:1.

7. A method as recited in claim 3 wherein the mobile fuel and thereducing agent are natural gas and the ratio of reducing agent to mobilefuel is between 1.5:1 and 2'1 8. A method as recited in claim 3 whereinthe mobile fuel and the reducing agent are natural gas and the ratio ofreducing agent to mobile fuel is 1.6221.

9. A method as recited in claim 3 wherein the reducing agent envelopsthe iiame and mixture and flows at a velocity of between 15 and 80% ofthe velocity of the ame.

10. A method of treating magnetite ore to produce metallic iron in afurnace having a reducing chamber and a molten metal bath beneath suchchamber comprising the steps of burning a mobile fuel in an excess ofoxygen to provide a downwardly directed flame zone Which is oxidizing incharacter, introducing a mixture of finely divided predominatelymagnetite ore and ux into the flame to be propelled thereby and rapidlyheat such mixture, thereafter introducing a reducing agent into intimatecontact with the ame and mixture suspended therein to ow concurrentlytherewith and reduce the iron oxide to metallic iron, impinging theproducts of combustion upon the surface of the bath to separate thegaseous constituents from the metallic iron and slag suspended therein,and conducting such gaseous constituents at an angle of substantially tothe direction of impingement of the products of combustion upon the bathto promote separation of the gaseous constituents from the iron andslag.

11. A method as recited in claim 10 wherein the gaseous constituents areconducted away from the surface of the bath at a velocity of not overtwo feet per second.

12. A method of treating magnetite ore to produce metallic iron in afurnace having a reducing chamber and a molten metal bath beneath suchchamber comprising the steps of burning a mobile fuel in an excess ofoxygen to provide a downwardly directed flame zone which is oxidizing incharacter and having a temperature of at least 2800 F., introducing amixture of iinely divided predominately magnetite ore and flux into theflame to be propelled thereby and to exothermically react with theexcess oxygen to produce ferric oxide, thereafter introducing a reducingagent to the mixture as suspended in the flame to reduce the ferricoxide to metallic iron, and impinging the products of combustion uponthe surface of the bath to separate the gaseous constituents from themetallic iron and slag suspended therein.

13. A method as recited in claim 12 wherein the mixture in the flame isheated to a temperature of about 3500 F. to 3600 F. before the mixtureis subjected to the reducing action.

14. A method as recited in claim 12 wherein the bath temperature is atleast 2800 F.

15. A method as recited in claim 12 wherein the velocity of the metalliciron and slag in the gaseous constituents impinge upon the surface ofthe bath at a velocity of at least 16 feet per second.

16. A method as recited in claim 12 wherein the mixture consists ofparticles not over about 60 mesh with less than 15% below about 325mesh.

17. The method of ash smelting of iron which comprises crushing iron oreand a flux to below 60 mesh but less than 15 below 325 mesh, feeding thecrushed ore and ux downwardly into a strongly oxidizing downwardlydirected flame maintained -so that the ore is entrained and carriedconcurrently with the flame and is heated to a temperature of about 3500F. to 3600 F., providing a reducing zone wherein the flame in which theore and ux is entrained is adjusted to strongly reducing conditions,separating the iron by impinging the flame in which the reduced ore isretained onto the surface of a bath of molten iron, withdrawing amaterial portion of the molten iron from the bath, adjusting its carboncontent to about 3% to 3.5%, and returning the withdrawn portion to thebath to promote final reduction of and removal of remaining oxygen fromthe bath.

18. The method of claim 17 wherein the portion of molten iron withdrawnfrom the bath is between 15% and 50% of the molten iron in the bath.

References Cited in the tile of this patent UNITED STATES PATENTS1,317,295 Hill Sept. 30, 1919 1,490,012 Kapteyn Apr. 8, 1924 2,526,659Harman Oct. 24, 1950 2,530,077 Ramsing Nov. 14, 1950 2,750,277 MarshallJune 12, 1956

1. A METHOD OF TREATING ORE TO PRODUCE METALLIC IRON IN A FURNACE HAVINGA REDUCING CHAMBER AND A MOLTEN METAL BATH BENEATH SUCH CHAMBERCOMPRISING THE STEPS OF BURNING A MOBILE FUEL WITH THE PRODUCTS OFCOMBUSTION OF SUCH BURNING DIRECTED DOWNWARDLY TO IMPINGE UPON THESURFACE OF THE BATH, INTRODUCING A MIXTURE OF FINELY DIVIDED IRON OREAND FLUX AXIALLY OF THE FLAME FROM THE BURNING FUEL TO BE PROPELLEDTHEREBY AND RAPIDLY HEAT SUCH MIXTURE, THEREAFTER ENVELOPING THE FLAMEAND THE MIXTURE SUSPENDED THEREIN WITH A GASEOUS STATE REDUCING AGENT TOFLOW CONCURRENTLY THEREWITH AND REDUCE THE IRON OXIDE IN THE ORE TOMETALLIC IRON, AND SEPARATING THE GASEOUS CONSTITUENTS FROM THE METALLICIRON AND SLAG SUSPENDED THEREIN BY THE IMPINGEMENT OF THE PRODUCTS OFCOMBUSTION UPON THE SURFACE OF THE BATH.